clc,clear
c4 = 2280/80*2*pi;
c0 = 1479/80*2*pi;
d = 25;
a = 0.120297;
D4 = (d+a)/2 * c4 + a/(4*pi) * c4^2
D0 = (d+a)/2 * c0 + a/(4*pi) * c0^2
D4-D0